This study shows the development and application of an analytical method for the determination of bisphenol A (BPA) in aqueous samples such as tap, river and mineral water and plastic leachates, based on an extensive literature search to understand the gaps for the determination of BPA in aqueous samples. We found that most of the methods in the literature employ some chromatographic strategy, and, to a much lesser extent, non-chromatographic instrumentation. In this scenario, we show an ultraviolet spectrophotometric-based method that can be used for routine analysis. Sample preparation was conducted by means of solvent extraction followed by back-extraction into an alkaline aqueous solution (liquid-liquid-liquid microextraction) and the detection was performed by UV spectrophotometry at 294 nm. Optimization of variables affecting both extraction and back-extraction was conducted, and the optimal extraction conditions were obtained: 85 mL aqueous sample buffered at pH 10, ionic strength adjusted with NaCl to a 2 mol L-1 final concentration, extraction with 6 mL of ethyl ether for 10 min and back-extraction into 0.5 mL of 2 mol L-1 aqueous NaOH. The following quality parameters were obtained: determination coefficient (R2) > 0.999, intra and inter-day repeatability better than 7.8% and 300 enhancement factor. The method was applied in different aqueous samples with excellent recovery and precision results, and no BPA was detected in natural water, even with the excellent limit of detection (3.5 μg L-1) and limit of quantification obtained. Limitations of this method involve analysis of samples with humic acid concentrations higher than 2 mg L-1 or high concentration of phenols and/or phthalate esters.

In this study, a method for determination of hexavalent chromium in aqueous samples using liquid-liquid microextraction (LLME) and detection by Flame Atomic Absorption Spectrometry (F AAS) was developed. The LLME procedure was based on the extraction of Cr (VI) by acetone at a sample pH of 1.2. The use of saturated ammonium sulphate solution allowed effective separation of the aqueous and organic phases and acetone extracted chromium. The sample pH, acetone volume and stirring time were optimized by a full factorial design.

Neste estudo é proposto um novo procedimento analítico para a determinação de fenóis em amostras de couro utilizando a técnica de microextração em fase sólida refrigerada internamente (CF-SPME) com derivatização direta na fibra e cromatografia gasosa acoplada a espectrometria de massas com monitoramento de íons selecionados (GC-SIM-MS). As condições experimentais para a extração e derivatização foram otimizadas utilizando procedimentos quimiométricos, sendo tempo de extração e temperatura da amostra de 5 min e 170 ºC, temperatura do recobrimento da fibra de 20 ºC, e exposição da fibra ao headspace de 70 µL do agente derivatizante bis(trimetilsilil)trifluor-acetamida por 23 min. Limites de detecção variaram entre 1,03 e 2,68 µg g-1 e o desvio padrão relativo (RSD) foi menor que 15% (n = 5). Estudos de recuperações em três níveis de concentração variaram entre 64,5 e 92,3%.

This study proposes a new analytical procedure based on an internally cooled solid phase microextraction technique (CF-SPME) combined with on-fiber derivatization and gas chromatography-selected ion monitoring-mass spectrometry (GC-SIM-MS) for the determination of phenols extracted directly from leather samples. The extraction and derivatization conditions were optimized using experimental designs, such as: extraction time and sample temperature of 5 min and 170 ºC, fiber recoat temperature of 20 ºC, and exposing the fiber to the headspace of 70 µL of bis(trimethylsylyl)trifluoro-acetamide derivatizing agent for 23 min. Detection limits ranging from 1.03 to 2.68 µg g-1 and relative standard deviation (RSD) lower than 15% (n = 5) were obtained. The recovery was studied at three concentration levels and excellent recoveries ranging from 64.5 to 92.3% were obtained.